I'm pretty certain that it has to be your own inheritance.
Otherwise the catch is far to easy to come by. Just go to the next antiquities store and pick up an old set of silver cutlery... it's most likely been inherited by someone at some point.
Getting something like that would have been easy for Marcone, but the states at some point that his parents where in no position to leave him anything, let alone anything made from silver.
Hence: Your own inheritance.
As for Murphy's gun, one might argue that by giving the instruction that others should take up her gun should she fall, she passes the gun to that person, making the bullets an inheritance once more.